Integrated memory comprising secondary access devices between digit lines and primary access devices

ABSTRACT

Some embodiments include an integrated assembly having a primary access transistor. The primary access transistor has a first source/drain region and a second source/drain region. The first and second source/drain regions are coupled to one another when the primary access transistor is in an ON mode, and are not coupled to one another when the primary access transistor is in an OFF mode. A charge-storage device is coupled with the first source/drain region. A digit line is coupled with the second source/drain region through a secondary access device. The secondary access device has an ON mode and an OFF mode. The digit line is coupled with the charge-storage device only when both the primary access transistor and the secondary access device are in their respective ON modes.

RELATED PATENT DATA

This patent is related to U.S. Provisional Application Ser. No. 62/717,636 which was filed Aug. 10, 2018.

TECHNICAL FIELD

Integrated memory comprising secondary access devices between digit lines and primary access devices.

BACKGROUND

Memory is utilized in modern computing architectures for storing data. One type of memory is Dynamic Random-Access Memory (DRAM). DRAM may provide advantages of structural simplicity, low cost and high speed in comparison to alternative types of memory.

DRAM may utilize memory cells which each have one capacitor in combination with one transistor (so-called 1T-1C memory cells), with the capacitor being coupled with a source/drain region of the transistor. An example 1T-1C memory cell 2 is shown in FIG. 1, with the transistor labeled T and the capacitor labeled C. The capacitor has one node coupled with a source/drain region of the transistor, and has another node coupled with a common plate, CP. The common plate may be coupled with any suitable voltage, such as a voltage within a range of from greater than or equal to ground to less than or equal to VCC (i.e., ground≤CP≤VCC). In some applications, the common plate is at a voltage of about one-half VCC (i.e., about VCC/2). The transistor has a gate coupled to a wordline WL (i.e., access line), and has a source/drain region coupled to a bitline BL (i.e., digit line or sense line). In operation, an electrical field generated by voltage along the wordline may gatedly couple the bitline to the capacitor during read/write operations.

Another prior art 1T-1C memory cell configuration is shown in FIG. 2. The configuration of FIG. 2 shows two memory cells 2 a and 2 b; with the memory cell 2 a comprising a transistor T1 and a capacitor C1, and with memory cell 2 b comprising a transistor T2 and a capacitor C2. Wordlines WL0 and WL1 are electrically coupled with the gates of transistors T1 and T2, respectively. A connection to a bitline BL is shared by the memory cells 2 a and 2 b.

The memory cells described above may be incorporated into memory arrays, and in some applications the memory arrays may have open bitline arrangements. An example integrated assembly 9 having open bitline architecture is shown in FIG. 3. The assembly 9 includes two laterally adjacent memory arrays (“Array 1” and “Array 2”), with each of arrays including memory cells of the type described in FIG. 2 (not labeled in FIG. 3 in order to simplify the drawing). Wordlines WL0-WL7 extend across the arrays, and are coupled with wordline drivers. Digit lines D0-D8 are associated with the first array (Array 1), and digit lines D0*-D8* are associated with the second array (Array 2). Sense amplifiers SA0-SA8 are provided between the first and second arrays. Digit lines at the same height are paired within one another and compared through a sense amplifier (e.g., digit lines D0 and D0* are paired with one another and compared with the sense amplifier SA0). In a read operation, one of the paired digit lines may serve as a reference in determining electrical properties (e.g., voltage) of the other of the paired digit lines.

Conventional DRAM accesses all memory cells along a row when a wordline is activated. In some applications it may be desirable to selectively access only some of the memory cells along the row, or even just a single memory cell (i.e., a single bit). It would be desirable to develop DRAM architectures which enable access of specific memory cells along an activated row.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a prior art memory cell having 1 transistor and 1 capacitor.

FIG. 2 is a schematic diagram of a pair of prior art memory cells which each have 1 transistor and 1 capacitor, and which share a bitline connection.

FIG. 3 is a schematic diagram of a prior art integrated assembly having open bitline architecture.

FIG. 4 is a diagrammatic cross-sectional side view showing a region of an example integrated assembly.

FIG. 5 is a schematic diagram illustrating a portion of an example memory array which may comprise the assembly of FIG. 4.

FIG. 6 is a schematic diagram illustrating an operation occurring within a region of the example memory array of FIG. 5.

FIG. 7 is a diagrammatic cross-sectional side view showing a region of an example integrated assembly which may be within the memory array of FIG. 5, and which may be a specific example of the more generic assembly of FIG. 4.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include integrated assemblies having memory cells which each include a primary access device (e.g., a first transistor) which gatedly couples a charge-storage device (e.g., a capacitor) with a digit line. The primary access devices are arranged in rows, and all of primary access devices along a given row are switched from an OFF mode to an ON mode when the row is activated. Secondary access devices (e.g., second transistors) are provided between the primary access devices and the digit lines. The secondary access devices may be utilized to selectively couple the digit lines to only specific memory cells along an activated row. Example embodiments are described with reference to FIGS. 4-7.

Referring to FIG. 4, a memory array 10 includes a plurality of memory cells 12. Each of the memory cells comprises a capacitor 16 and a transistor 18. The capacitors 16 may be considered to be examples of charge-storage devices which may be utilized in the memory cells 12. In other embodiments, other suitable charge-storage devices may be utilized; with examples of other suitable charge-storage devices including phase change materials, conductive-bridging materials, etc. The transistors 18 are access devices, and may be referred to as primary access devices (or as primary access transistors) to distinguish them from other access devices discussed below.

The capacitors 16 have nodes connected to reference structures 19. The reference structures may comprise any suitable voltage, and in some embodiments may correspond to common plates of the type described above with reference to FIGS. 1 and 2.

The primary access devices 18 and capacitors 16 are supported by a base 30 comprising semiconductor material 32. The semiconductor material 32 may comprise any suitable composition(s); and in some embodiments may comprise, consist essentially of, or consist of one or more of silicon, germanium, III/V semiconductor material (e.g., gallium phosphide), semiconductor oxide, etc.; with the term III/V semiconductor material referring to semiconductor materials comprising elements selected from groups III and V of the periodic table (with groups III and V being old nomenclature, and now being referred to as groups 13 and 15). For instance, the semiconductor material 32 may comprise, consist essentially of, or consist of monocrystalline silicon.

The base 30 may be referred to as a semiconductor substrate. The term “semiconductor substrate” means any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductor substrates described above. In some applications, the base 30 may correspond to a semiconductor substrate containing one or more materials associated with integrated circuit fabrication. Such materials may include, for example, one or more of refractory metal materials, barrier materials, diffusion materials, insulator materials, etc.

The illustrated primary access transistors have gates 20 along wordlines WL0-WL3, and have source/drain regions 22 extending into the semiconductor material 32 of the base 30. The source/drain regions may comprise conductively-doped regions within the semiconductor material 32.

The gates 20 are spaced from the semiconductor material 32 by dielectric material (i.e., insulative material) 24. The dielectric material 24 may comprise any suitable composition(s); and in some embodiments may comprise, consist essentially of, or consist of silicon dioxide. The dielectric material 24 may be referred to as gate dielectric material.

The primary access transistors 18 have channel regions 26 beneath the gates 20; and the source/drain regions of each of the transistors are gatedly coupled to one another through the channel region between them. In the illustrated embodiment, the channel regions 26 extend horizontally between the source/drain regions 22.

The capacitors 16 are coupled with vertically-extending interconnects 28, which in turn are coupled with some of the source/drain regions 22. Others of the source/drain regions 22 are coupled with a digit line DL0 through vertically-extending interconnects 34. The interconnects 28 and 34 may comprise any suitable electrically conductive composition(s); such as, for example, one or more of various metals (e.g., titanium, tungsten, cobalt, nickel, platinum, ruthenium, etc.), metal-containing compositions (e.g., metal silicide, metal nitride, metal carbide, etc.), and/or conductively-doped semiconductor materials (e.g., conductively-doped silicon, conductively-doped germanium, etc.).

The digit line DL0 extends to a sense amplifier SA0.

The primary access transistors 18 are in paired relationships such that two adjacent transistors share a common connection to the digit line DL0. For instance, two of the primary access transistors are labeled as 18 a and 18 b, and such primary access transistors are paired with one another. The primary access transistors 18 a and 18 b may be referred to as first and second primary access transistors, respectively. The primary access transistors 18 a and 18 b together comprise three source/drain regions (labeled 22 a, 22 b and 22 c). The source/drain regions 22 a, 22 b and 22 c may be referred to as first, second and third source/drain regions respectively. The second source/drain region 22 b is shared between the first and second primary access transistors 18 a and 18 b, and is coupled with the digit line DL0. The first source/drain region is coupled with a first capacitor (labeled 16 a), and the third source/drain region is coupled with a second capacitor (labeled 16 b).

The channel regions of the first and second primary access transistors 18 a and 18 b are labeled 26 a and 26 b, and may be referred to as first and second channel regions, respectively.

The memory cells comprising the first and second primary access transistors 18 a and 18 b are labeled as memory cells 12 a and 12 b, and may be referred to as first and second memory cells, respectively.

In operation, each of the primary access transistors (e.g., transistor 18 a) has an OFF mode and an ON mode. The ON mode is a state in which there is a sufficient electric field applied to the channel region of the primary access transistor (e.g., channel region 26 a) so that the channel region couples the source/drain regions of the transistor (e.g., the source/drain regions 22 a and 22 b) with one another. The OFF mode is a state in which there is insufficient electric field applied to the channel region of the primary access transistor to couple the source/drain regions of the primary access transistor to one another. The primary access transistors are along rows (i.e., the rows defined by the wordlines WL0, WL1, WL2 and WL3). When a row is activated, sufficient voltage is applied along the wordline of the row so that all of the primary access transistors along the row are switched from the OFF mode to the ON mode; and when rows are not activated the transistors along the rows are in the OFF mode.

Isolation material 36 extends into the base 30 and separates paired-transistor arrangements from one another. The isolation material 36 may comprise any suitable composition(s); and in some embodiments may comprise, consist essentially of, or consist of silicon oxide.

In conventional DRAM configurations, the digit line DL0 would be directly coupled to source/drain regions of the primary access transistors (e.g., would be directly coupled to the source/drain region 22 b). When a row is activated (e.g., the row comprising wordline WL0), all of the primary access transistors along the row (e.g., the primary access transistor 18 a) are transitioned from the OFF mode to the ON mode (e.g., the gate 20 a would provide a suitable electric field across the channel 26 a to couple the source/drain regions 22 a and 22 b), and all memory cells along such row (e.g., memory cell 12 a) now have their capacitor (e.g., capacitor 16 a) coupled to a digit line (e.g., DL0). In contrast, the illustrated embodiment of FIG. 4 has components 40 provided along the interconnects 34 to control current flow along the interconnects 34, and to provide a mechanism for selecting specific memory cells along an activated row.

The illustrated components 40 may be referred to as secondary access devices, and in the embodiment of FIG. 4 are shown to be secondary access transistors.

The interconnects 34 are shown to include pillars 42 of semiconductor material 44. The pillars 42 extend vertically, and may be referred to as vertically-extending lengths of the semiconductor material 44. In other embodiments, the lengths of semiconductor material 44 may extend in directions other than vertically.

In the shown embodiment, each of the interconnects 34 includes a first conductive material 46 under the semiconductor material 44. The first conductive material 46 may comprise any suitable electrically conductive composition(s); such as, for example, one or more of various metals (e.g., titanium, tungsten, cobalt, nickel, platinum, ruthenium, etc.), metal-containing compositions (e.g., metal silicide, metal nitride, metal carbide, etc.), and/or conductively-doped semiconductor materials (e.g., conductively-doped silicon, conductively-doped germanium, etc.). In some embodiments, the first material 46 may comprise a same composition as the semiconductor material 44, and may be a conductively-doped extension of the semiconductor material 44.

The semiconductor material 44 may comprise any suitable composition(s); and in some embodiments may comprise, consist essentially of, or consist of one or more of silicon, germanium, III/V semiconductor material (e.g., gallium phosphide), semiconductor oxide, etc.; with the term III/V semiconductor material referring to semiconductor materials comprising elements selected from groups III and V of the periodic table (with groups III and V being old nomenclature, and now being referred to as groups 13 and 15). In some example embodiments, the semiconductor material 44 may comprise polycrystalline silicon.

In some embodiments, the materials 44 and 46 may be considered together to form the interconnects 34 which extend between the source/drain regions 22 and the digit line DL0. One of the interconnects 34 is labeled as 34 a, and is coupled with the second source/drain region 22 b. The secondary access transistor coupled with the interconnect 34 a is labeled 40 a.

The secondary access transistors 40 include conductive gating material 48, and include insulative material 50 between the gating material 48 and the semiconductor material 44 of the pillars 42.

The gating material 48 may comprise any suitable electrically conductive composition(s); such as, for example, one or more of various metals (e.g., titanium, tungsten, cobalt, nickel, platinum, ruthenium, etc.), metal-containing compositions (e.g., metal silicide, metal nitride, metal carbide, etc.), and/or conductively-doped semiconductor materials (e.g., conductively-doped silicon, conductively-doped germanium, etc.). The gating material 48 is configured as transistor gates 49.

The insulative material 50 may comprise any suitable composition(s); and in some embodiments may comprise, consist essentially of, or consist of silicon dioxide. The insulative material 50 may be referred to as gate dielectric material in some embodiments.

The secondary access transistors 40 comprise source/drain regions 52 and 54, and channel regions 56 between the source/drain regions. The source/drain regions 54 may be referred to as upper source/drain regions, and the source/drain regions 52 may be referred to as lower source/drain regions. The channel regions 56 extend vertically between the upper and lower source/drain regions. In some embodiments, the secondary access transistors 40 may be referred to as vertical transistors due to the vertically-extending channel regions 56; and the primary access transistors 18 may be referred to as planar transistors due to the horizontally-extending channel regions 26. In some embodiments, the primary access transistor 18 a may be considered to have first and second source/drain regions 22 a and 22 b which are spaced from one another by a horizontally-extending channel region 26 a; and the secondary access transistor 40 a may be considered to comprise third and fourth source/drain regions 52 a and 54 a which are spaced from one another by a vertically-extending channel region 56 a.

The channel regions 56 correspond to gated portions of the pillars 42 (i.e., to gated portions of the lengths of semiconductor material 44). In some embodiments, the channel regions 56 may be referred to as gated portions of the interconnects 34.

In some embodiments, the first and second access transistors 18 a and 18 b may be considered to comprise first and second gates 20 a and 20 b, respectively; and the secondary transistor 40 a may be considered to comprise a third gate 49 a. In the shown embodiment, the third gate 49 a is over the first and second gates 20 a and 20 b, and is under the digit line DL0.

In some embodiments, the secondary access transistors 40 may be considered to be examples of switches which control current flow along the interconnects 34. Such switches may be closed to enable access of the digit line DL0. In the shown embodiment, the “closing” of such switches corresponds to providing appropriate voltages to the gates 49 to enable current flow across the channel regions 56 between the source/drain regions 52 and 54.

In some embodiments, the components 40 may be considered to comprise an OFF mode and an ON mode. The ON mode is a state in which there is a sufficient electric field applied to the channel region of the secondary access transistor (e.g., channel region 56 a) so that the channel region couples the source/drain regions of the transistor (e.g., the source/drain regions 52 a and 54 b) with one another. The OFF mode is a state in which there is insufficient electric field applied to the channel region of the secondary access transistor to couple the source/drain regions of the secondary access transistor to one another. In embodiments in which the components 40 are considered to correspond to switches, the OFF mode is a state in which a switch is “open”, and the ON mode is a state in which the switch is “closed”.

A memory cell (e.g., memory cell 12 a) is only accessed when the associated primary access device (e.g., device 18 a) is in the ON mode and the associated secondary access device (e.g., device 40 a) is in the ON mode. In other words, the capacitor of the memory cell (e.g., capacitor 16 a) is only coupled to an associated digit line (e.g., DL0) when both the primary access device (e.g., 18 a) and the secondary access device (e.g., 40 a) are in their respective ON modes. Otherwise, the capacitor of the memory cell is isolated from the associated digit line.

The secondary access transistors 40 may be controlled with any suitable circuitry. FIG. 4 shows the gates 49 of the secondary access transistors incorporated into multiplexer (mux) circuitry, and coupled with a multiplexer driver (shown as a MUX DRIVER). Such enables each of the secondary access transistors to be separately controlled relative to the others.

The various components of FIG. 4 may have any suitable architectural relationships relative to one another. For instance, although the embodiment of FIG. 4 shows the third gate 49 a over the first and second gates 20 a and 20 b, and shows the digit line DL0 over the third gate; in other embodiments, the digit line may be placed in any other suitable location, and the various gates 20 a, 20 b, 49 a etc., may be placed in any suitable orientation relative to one another.

The memory cells 12 may be representative of a large number of substantially identical memory cells within a DRAM array; with the term “substantially identical” meaning identical to within reasonable tolerances of fabrication and measurement. FIG. 5 schematically illustrates a portion of the memory array 10, and shows a large number of substantially identical memory cells 12. Each of the memory cells comprises a primary access transistor 18 (only some of which are labeled), and a capacitor 16 (only some of which are labeled). The wordlines WL0-WL3 extend along rows of the memory array, and are coupled with gates of the primary access transistors 18. Each of the wordlines is coupled with a row driver. Digit lines DL0-DL3 extend along columns of the array and are coupled to the memory cells 12 through the secondary access transistors 40 (only some of which are labeled). The digit lines DL0-DL3 are coupled with sense amplifiers SA0-SA3.

The gates 49 (only some of which are labeled) of the secondary access transistors 40 are coupled with a multiplexer (mux) circuitry so that each of the secondary access transistors may be separately controlled. Specifically, the gates of the secondary access transistors 40 are coupled with mux lines (MUX0, MUX1, MUX2 and MUX3) which extend to a mux driver (shown as MUX DRIVER). The mux driver may be configured to address each of the gates 49 independently of the others.

An example operation utilized to specifically access one of the memory cells of the array 12 is described with reference to FIG. 6. The figure shows a schematic illustration of a region of the memory array 10, and shows the secondary access devices configured as switches to simplify the representation of OFF and ON modes of such devices. The various memory cells are labeled as 12 a-12 h so that they may be specifically identified relative to one another. Similarly, the various primary access gates are labeled 18 a-18 h, and the secondary access gates are labeled 40 a-40 d. The mux lines are labeled as MUXa, MUXb, MUXc and MUXd.

The wordlines WL0, WL1 and WL3 are shown to be OFF (i.e., not activated), and accordingly the primary access devices along such wordlines (devices 18 a, 18 b, 18 d, 18 e, 18 f and 18 h) would also be OFF. The wordline WL2 is shown to be ON (i.e., activated), and accordingly the primary access devices along such wordline (devices 18 c and 18 g) would also be ON.

The secondary access devices 40 a and 40 c are shown to be OFF, as represented by the shown switches being in open positions. The secondary access device 40 d is also OFF, but the secondary access device 40 b is ON (as represented by the shown switch being in a closed position). Thus the memory cell 12 c is specifically selected. The ability to select one or more specific memory cells along an activated row may advantageously enable reduced power consumption as compared to conventional devices in that not all of the memory cells along the activated row are dumping data to their respective digit lines and needing to be restored. Also, the ability to select one or more memory cells with the secondary access devices 40 and the mux driver may enable a common sense amplifier to be shared amongst several digit lines. Such is diagrammatically illustrated in FIGS. 5 and 6 with dashed lines extending to an optional common sense amplifier (shown as common SA) which may be utilized in place of SA0, SA1, SA2 and SA3. In some applications, all of the digit lines of a memory array may extend to the common sense amplifier.

The capacitors 16 of FIG. 4 may have any suitable configuration. FIG. 7 shows a region of the memory array 10 analogous to that of FIG. 4, but illustrating a specific example configuration of the capacitors 16. Each of the capacitors 16 comprises a first conductive node 58, a second conductive node 60, and an insulative material 62 between the first and second conductive nodes. The first and second conductive nodes 60 and 62 may comprise any suitable electrically conductive composition(s); such as, for example, one or more of various metals (e.g., titanium, tungsten, cobalt, nickel, platinum, ruthenium, etc.), metal-containing compositions (e.g., metal silicide, metal nitride, metal carbide, etc.), and/or conductively-doped semiconductor materials (e.g., conductively-doped silicon, conductively-doped germanium, etc.). The first and second conductive nodes may comprise the same composition as one another, or may comprise different compositions relative to one another. The insulative material 62 may comprise any suitable composition(s), and in some embodiments may comprise, consist essentially of, or consist of silicon dioxide.

In the shown embodiment, the lower conductive nodes 58 are configured as upwardly-opening containers. In other embodiments, the lower conductive nodes may have other suitable shapes. The lower conductive nodes 58 may be referred to as storage nodes, and the upper nodes 60 may be referred to as plate electrodes. In some embodiments, the plate electrodes within memory array 10 may all be coupled to one another, and may be coupled to a reference voltage (e.g., the common plate voltage).

The assemblies and structures discussed above may be utilized within integrated circuits (with the term “integrated circuit” meaning an electronic circuit supported by a semiconductor substrate); and may be incorporated into electronic systems. Such electronic systems may be used in, for example, memory modules, device drivers, power modules, communication modems, processor modules, and application-specific modules, and may include multilayer, multichip modules. The electronic systems may be any of a broad range of systems, such as, for example, cameras, wireless devices, displays, chip sets, set top boxes, games, lighting, vehicles, clocks, televisions, cell phones, personal computers, automobiles, industrial control systems, aircraft, etc.

Unless specified otherwise, the various materials, substances, compositions, etc. described herein may be formed with any suitable methodologies, either now known or yet to be developed, including, for example, atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etc.

The terms “dielectric” and “insulative” may be utilized to describe materials having insulative electrical properties. The terms are considered synonymous in this disclosure. The utilization of the term “dielectric” in some instances, and the term “insulative” (or “electrically insulative”) in other instances, may be to provide language variation within this disclosure to simplify antecedent basis within the claims that follow, and is not utilized to indicate any significant chemical or electrical differences.

The particular orientation of the various embodiments in the drawings is for illustrative purposes only, and the embodiments may be rotated relative to the shown orientations in some applications. The descriptions provided herein, and the claims that follow, pertain to any structures that have the described relationships between various features, regardless of whether the structures are in the particular orientation of the drawings, or are rotated relative to such orientation.

The cross-sectional views of the accompanying illustrations only show features within the planes of the cross-sections, and do not show materials behind the planes of the cross-sections, unless indicated otherwise, in order to simplify the drawings.

When a structure is referred to above as being “on”, “adjacent” or “against” another structure, it can be directly on the other structure or intervening structures may also be present. In contrast, when a structure is referred to as being “directly on”, “directly adjacent” or “directly against” another structure, there are no intervening structures present.

Structures (e.g., layers, materials, etc.) may be referred to as “extending vertically” to indicate that the structures generally extend upwardly from an underlying base (e.g., substrate). The vertically-extending structures may extend substantially orthogonally relative to an upper surface of the base, or not.

Some embodiments include an integrated assembly having a primary access transistor. The primary access transistor has a first source/drain region and a second source/drain region. The first and second source/drain regions are coupled to one another when the primary access transistor is in an ON mode, and are not coupled to one another when the primary access transistor is in an OFF mode. A charge-storage device is coupled with the first source/drain region. A digit line is coupled with the second source/drain region through a secondary access device. The secondary access device has an ON mode and an OFF mode. The digit line is coupled with the charge-storage device only when both the primary access transistor and the secondary access device are in their respective ON modes.

Some embodiments include an integrated assembly which comprises a first primary access transistor and a second primary access transistor. The first primary access transistor comprises a first gate proximate a first channel region, and the second primary access transistor comprises a second gate proximate a second channel region. The first and second primary access transistors together comprise three source/drain regions, with one of the three source/drain regions being shared by the first and second primary access transistors. The three source/drain regions are a first source/drain region, a second source/drain region and a third source/drain region. The first and second source/drain regions are gatedly coupled to one another through the first channel region. The second and third source/drain regions are gatedly coupled to one another through the second channel region. A first charge-storage device is coupled with the first source/drain region. A second charge-storage device is coupled with the third source/drain region. A digit line is coupled with the second source/drain region through an interconnect. A switch controls current flow along the interconnect.

Some embodiments include an integrated assembly which comprises a first primary access transistor and a second primary access transistor. The first primary access transistor comprises a first gate proximate a first channel region, and the second primary access transistor comprises a second gate proximate a second channel region. The first and second primary access transistors together comprise three source/drain regions, with one of the three source/drain regions being shared by the first and second primary access transistors. The three source/drain regions are a first source/drain region, a second source/drain region and a third source/drain region. The first and second source/drain regions are gatedly coupled to one another through the first channel region. The second and third source/drain regions are gatedly coupled to one another through the second channel region. The first channel region extends horizontally between the first and second source/drain regions. The second channel region extends horizontally between the second and third source/drain regions. A first capacitor is coupled with the first source/drain region. A second capacitor is coupled with the third source/drain region. A digit line is coupled with the second source/drain region through an interconnect. The interconnect comprises a vertically-extending pillar of a semiconductor material. A secondary access transistor gates a portion of the vertically-extending pillar of the semiconductor material.

In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents. 

We claim:
 1. An integrated assembly, comprising: a primary access transistor having a first source/drain region and a second source/drain region which are coupled to one another when the primary access transistor is in an ON mode, and which are not coupled to one another when the primary access transistor is in an OFF mode; a charge-storage device coupled with the first source/drain region; and a digit line coupled with the second source/drain region through a secondary access device; the secondary access device having an ON mode and an OFF mode; the digit line being coupled with the charge-storage device only when both the primary access transistor and the secondary access device are in their respective ON modes.
 2. The integrated assembly of claim 1 wherein the secondary access device is a secondary access transistor.
 3. The integrated assembly of claim 2 wherein: the primary access transistor has a first channel region which extends horizontally between the first and second source/drain regions; and the secondary access transistor has a second channel region which extends vertically between a third source/drain region and a fourth source/drain region.
 4. The integrated assembly of claim 1 wherein the charge-storage device is a capacitor.
 5. The integrated assembly of claim 1 wherein the primary access transistor and the charge-storage device together comprise a memory cell, and wherein the memory cell is one of many substantially identical memory cells within a DRAM array.
 6. The integrated assembly of claim 5 wherein the digit line is one of many digit lines extending along columns of the DRAM array, and wherein at least some of the digit lines extend to a common sense amplifier.
 7. An integrated assembly, comprising: a first primary access transistor and a second primary access transistor; the first primary access transistor comprising a first gate proximate a first channel region, and the second primary access transistor comprising a second gate proximate a second channel region; the first and second primary access transistors together comprising three source/drain regions; the three source/drain regions being a first source/drain region, a second source/drain region and a third source/drain region; the first and second source/drain regions being gatedly coupled to one another through the first channel region; the second and third source/drain regions being gatedly coupled to one another through the second channel region; a first charge-storage device coupled with the first source/drain region; a second charge-storage device coupled with the third source/drain region; a digit line coupled with the second source/drain region through an interconnect; and a switch controlling current flow along the interconnect.
 8. The integrated assembly of claim 7 wherein the interconnect comprises a length of a semiconductor material.
 9. The integrated assembly of claim 8 wherein the switch controls current flow along the length of the semiconductor material.
 10. The integrated assembly of claim 9 wherein the switch is a secondary access transistor.
 11. The integrated assembly of claim 10 wherein the secondary access transistor comprises a third gate which is electrically coupled with a multiplexer driver.
 12. The integrated assembly of claim 7 wherein the first and second primary access transistors and the first and second charge-storage devices are comprised by memory cells, and wherein the memory cells are two of many substantially identical memory cells within a DRAM array.
 13. The integrated assembly of claim 12 wherein the digit line is one of many digit lines extending along columns of the DRAM array, and wherein at least some of the digit lines extend to a common sense amplifier.
 14. The integrated assembly of claim 7 wherein the first and second charge-storage devices are first and second capacitors, respectively.
 15. An integrated assembly, comprising: a first primary access transistor and a second primary access transistor; the first primary access transistor comprising a first gate proximate a first channel region, and the second primary access transistor comprising a second gate proximate a second channel region; the first and second primary access transistors together comprising three source/drain regions; the three source/drain regions being a first source/drain region, a second source/drain region and a third source/drain region; the first and second source/drain regions being gatedly coupled to one another through the first channel region; the second and third source/drain regions being gatedly coupled to one another through the second channel region; the first channel region extending horizontally between the first and second source/drain regions; the second channel region extending horizontally between the second and third source/drain regions; a first capacitor coupled with the first source/drain region; a second capacitor coupled with the third source/drain region; a digit line coupled with the second source/drain region through an interconnect; the interconnect comprising a vertically-extending pillar of a semiconductor material; and a secondary access transistor gating a portion of the vertically-extending pillar of the semiconductor material.
 16. The integrated assembly of claim 15 wherein the first and second primary access transistors and the first and second capacitors are comprised by memory cells, and wherein the memory cells are two of many substantially identical memory cells within a DRAM array.
 17. The integrated assembly of claim 16 wherein the digit line is one of many digit lines extending along columns of the DRAM array, and wherein at least some of the digit lines extend to a common sense amplifier.
 18. The integrated assembly of claim 15 wherein the secondary access transistor comprises a third gate; and wherein the third gate is over the first and second gates.
 19. The integrated assembly of claim 18 wherein the digit line is over the third gate.
 20. The integrated assembly of claim 18 wherein the third gate is part of a multiplexer circuit and is coupled with a multiplexer driver. 